Vandals are said to be responsible for destroying a number of Commonwealth War Grave Commission headstones in a U.K. cemetery days before the commemoration of the D-Day landings.

“Sad to report that a number of gravestones in Hirst Wood Cemetery have been smashed,” read a statement issued by the cemetery Thursday.

“It is impossible to understand the callous thoughtlessness of those who did this. Do they boast to their friends and [relatives] that they managed to smash gravestones? What possible satisfaction can they get from such a mindless act?”

Police believe the gravestones at Hirst Wood Burial Ground in West Yorkshire, England, were smashed sometime between Monday and Tuesday.

The war graves on the site are maintained by the U.K.’s Commonwealth War Graves Commission, who police say will repair the damaged headstones.

“Our investigation is ongoing into the vandalism of these gravestones. They were destroyed in what was a mindless act of destruction and I would urge anyone with any information to come forward and speak to the police,” read a statement from West Yorkshire Police.

“High visibility reassurance patrols have been stepped up in the area whilst officers continue with their enquiries.”